Denitrification of hydrocarbons



United States Patent Ofifice 3,30%,3fi9 Patented Mar. 14, 1967 3,309,309 ENITREFICATION F HYDRGCARBQNS Fritz Karl Hess, Pointe Claire, Quebec, (Ianada, assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed May 27, 1965, er. No. 459,428 18 Claims. (Cl. 208254) This invention relates to a new and improved method of refining nitrogen-containing hydrocarbon materials. More particularly, this invention relates to a process for removing nitrogen compounds from hydrocarbon oils by means of an improved extraction procedure.

The presence of nitrogen compounds, such as pyrroles, pyridines, quinolines, pyrazoles, aryl and alkyl amines, etc., is disadvantageous for many reasons. When these compounds are present in hydrocarbon oils such as lubricating oils, fuel oils, diesel oils, jet fuels, gasolines, etc, they may cause color loss, organic sedimentation upon storage, sludge and gum formations, and the like. Furthermore, upon subsequent catalytic treatment, catalyst posioning is common. Accordingly, in order to avoid these adverse effects, it is frequently desirable to remove such nitrogen compounds and various procedures directed to this purpose are known to the art. For example, it is known to remove nitrogen-containing compounds by complexing with transition metal salts, by various extraction procedures using selective solvents, by adsorption procedures, acid treating, hydrofining, incorporation of additives, etc. These procedures have, however, met with limited success and'are often unsatisfactory and erratic. The most valuable procedure has proven to be hydrofining which requires the use of a hydrogenation catalyst. Hydr-ofining suffers the disadvantage, however, of hydro genating valuable high-octane producing components, which in the case of gasoline treatment is obviously to be avoided. Acid extraction, such as sulfuric extraction, has also been used extensively, but is subject to the drawbacks of gum formation and corrosion. The adsorption procedures have not generally proved attractive on a commercial scale because of the difficulty in desorbing adsorbed materials, and in the cost of regenerating the adsorbent.

It is therefore the purpose of the present invention to provide an improved process for the removal of nitrogen compounds from hydrocarbon materials, particularly petroleum distillates. The removal of nitrogen-containing compounds according to the invention is accomplished by contacting the oil with an organic sulfoxide containing a minor amount of a nitrophenol and separating a hydrocarbon phase having a reduced basic nitrogen content.

Organic sulfoxides constitute a recognized class of organic compounds. In R. E. Kirk et al., Encyclopedia of Chemical Technology, volume 13, pages 353-357 (1954), a disclosure is provided of sulfoxides as a class and specific members of the group. The aliphatic sulfoxides, e.g., C to C sulfoxides, particularly dimethyl sulfoxide, will be preferred according to the invention. However, cycloaliphatic and cyclic sulfoxides such as cyclotetrarnethylene sulfoxide and dihydro-l-thiophene oxide can also be used in the invention.

Organic sulfoxides, such as dimethyl sulfoxide, are known agents in hydrocarbon treating processes for various purposes. For example, US. 3,154,576 discloses the use of dimethyl sulfoxide for suifonate extraction, and US. 2,927,076 discloses similar use in removing sulfonic acids from petroleum oil. The present invention, however, is predicated on the discovery that inclusion of a minor amount, e.g., about 0.5 to 20 wt. percent, preferably about 05 to 5 wt. percent, of certain nitrophenols based on the weight of the sulfoxide, will remarkably improve the sulfoxides ability to remove nitrogen-containing compounds.

The nitrophenols suitable in the present invention will be characterized by at least one hydroxy group and at least two nitro groups, the latter preferably being located at the even-numbered positions on the benzene ring. Exemplary compounds will include 2,4-dinitrophenol, 2,6- dinitrophenol, 2,4 dihydroxy 1,3,5 trinitrobenaene (styphnic acid), and 2,4,6-trinitrophenol (picric acid). The particularly preferred nitrophenol will be 2,4,6- trinitrophenol (picric acid).

In general the present process will be applicable to any hydrocarbon feedstock containing nitrogen impur ties. Most commonly the feedstock will be petroleum-derived, such as gasoline, naphtha, kerosene, diesel fuels, fuel o ls, catalytically cracked cycle stocks, catalytic heating OllS, catalytically cracked naphthas, heavy atmospheric gas oils, etc. The nitrogen content of the feedstock can range up to about 500 ppm. or higher, preferably up to about 200 p.p.rn.

The amount of the organic sulfoxide, e.g., dimethyl sulfoxide, required for the removal of the nitrogen impurities will vary with the character of the oil and its nitrogen content. Generally, the amount of sulfoxide solvent utilized should be sufficient to form a two-phase system. Typical proportions of the sulfoxide will usually fall within the range of about 5 to about 50 wt. percent, preferably about 5 to about 20 wt. percent, based on the hydrocarbon feed. The extraction process of the invention may be effected in any suitable manner, such as by batch or continuous type operation. When a batch-type operation is used, the hydrocarbon feed containing the nitrogen impurity is placed in an appropriate vessel equipped with suitable agitation means, the sulfoxidenitrophenol solution is added to the feedstock, and the mixture is thoroughly agitated for a predetermined period of time. The temperature at which the extraction is carried out is not critical, e.g., temperatures of 60 to 140 F. can be used, with ambient temperature being preferred. If elevated temperature is used, sufiicient pressure should be maintained within the extraction zone to prevent substantial volatilization of the feedstock or the solvent under the liquid-liquid extraction conditions. It will be obvious, therefore, that the pressure and temperature are related variables. Usually, pressures within the range of about 0 to about p.s.i.g. are sufficient, with atmospheric pressure being preferred. The contacting of the hydrocarbon feed stock and the sulfoxide-nitrophenol solution is carried out for a sufficient period of time to accomplish the desired extraction efiiciency which can be readily determined. Typical time periods range from about 1 minute to 2 hours, e.g., 2 to 30 minutes. After the mixing period, the mixture is allowed to stand until the two immiscible layers have separated. The extract phase containing nitrogen impurities can be treated for removal of the sulfoxide by suitable means, such as by distillation. The hydrocarbon rafiinate phase, having a substantially reduced nitrogen content, is preferably washed with water by batch or column-wise operation to remove traces of the sulfoxide and the nitrophenol. If desired, the treated hydrocarbon phase, after washing, can be finally filtered to remove any sediment.

It will be appreciated that conventional extraction procedures using known types of solvent extraction equipment can be used in the present invention, and that the above description is subject to conventional variations obvious to those skilled in the art.

The invention will be further illustrated by the following example which is not intended to be limiting.

Example A solvent solution of dimethyl sulfoxide containing 1 wt. percent picric acid (2,4,6-trinitrophenol) was prepared. The solution was used in the extraction of nitrogen impurities from three different hydrocarbon feedstocks; namely, a light catalytic naphtha, a light catalytically cracked naphtha, and a light coker naphtha. The basic nitrogen content of each of these feeds is indicated in the table below. Each feed was contacted at atmospheric pressure and ambient temperature, with an amount of the sulfoxide-picric acid solution equal to wt. percent of the feed. The contacting was continued, with agi tation, for about 3 minutes. After allowing sufiicient time for the immiscible layers to separate, the oil layer was separated from the extract layer and washed with water, and filtered. In each case the final oil layer was analyzed for basic nitrogen content, with the values determined being compared to the initial basic nitrogen content in the table below. For further comparison, identical extractions were carried out using aqueous picric acid solution (1 wt. percent picric acid in water), and relatively pure dimethylsulfoxide without added picric acid. The results of these experiments are sumarized in the following table.

6. The process of claim 5, wherein said nitrophenol is 2,4,6-trinitrophenol.

7. The process of claim 1, wherein said organic sulfoxide is dimethylsulfoxide and said nitrophenol is 2,4,6- trinitr-ophenol.

S. The process of claim 7, wherein said feed contains naphtha fractions.

9. The process of claim 7, wherein said solution contains a minor amount of said 2,4,6-trinitrophenol.

10. The process of claim 9, wherein said minor amount is within the range of about 0.5 to wt. percent, based on the weight of the sulfoxide.

11. The process of claim 10, wherein the amount of said solution used is about 5 to 50 wt. percent, based on the weight of said hydrocarbon feed.

12. The process for the removal of basic nitrogen compounds from petroleum hydrocarbons which comprises contacting said hydrocarbons with a solution comprising a major amount of dimethylsulfoxide and a minor amount of picric acid, and separating a hydrocarbon phase having a substantially reduced basic nitrogen content.

REDUCTION OF BASIC NITROGEN CONTENT WITH DIMETHYL SULFOXIDE-PICRIG ACID Product After Extraction Feed Before Extraction Dirncthylsulfoxide Dirnethylsulfoxide plus Water plus Picric Acid Solvent B asic Pieric Acid Nitrogen p.p.m.

Basic Percent Basic Basic Percent Basic Basic Percent Basic Nitrogen Nitrogen Nitrogen N itrogeu Nitrogen Nitrogen p.p.n1. Reduction p.p.n1. Reduction p.p.m. Reduction Light Catalytic Naphtha 9 74 1 97 4 89 Light Catalytic Cracked N aptha 43 18 58 3 93 11 74 Light Coker Naphtha 44 27 3 2 95 6 86 As indicated above, the dimethylsulfoxide solution containing added picric acid was a substantially improved basic nitrogen removal agent as compared to the pure dimethylsulfoxide or the aqueous picric acid solution. In all three cases, the basic nitrogen content of the feed was well over 90% reduced, as compared to substantially lower values with the other two comparative reagents.

What is claimed is:

1. A process for treating hydrocarbon feed which comprises contacting said feed with a solution comprising an organic sultoxide and a nitrophenol, and recovering a hydrocarbon phase having a substantially reduced nitrogen content.

2. The process of claim 1, wherein said organic sulfoxide is a C -C aliphatic sulfoxide.

3. The process of claim 2, wherein said organic sulfoxide is dimethylsulfoxide.

4. The process of claim 1, wherein said nitrophenol I has at least two nitro groups located at even-numbered positions on its benzene ring.

5. The process of claim 1, wherein said nitrophenol is selected from the group consisting of 2,4-dinitrophenol, 2,6 dinitrophenol, 2,4 dihydroxy 1,3,5-trinitrobenzene and 2,4,6-trinitrophenol,

13. The process of claim 12, wherein said minor amount is about 0.5 to 5 wt. percent, based on the weight of said dimethylsulfoxide.

14. The process of claim 13, wherein the amount of said solution used is about 5 to 20 wt. percent, based on the weight of said hydrocarbons.

15. The process of claim 14, wherein said petroleum hydrocarbons include naphtha fractions.

16. The process of claim 14, wherein said hydrocarbons include middle distillate fractions.

17. The process of claim 14, wherein said hydrocarbons include gas oil fractions.

18. The process of claim 14 which additionally cornprises water washing said hydrocarbon phase.

References Cited by the Examiner UNITED STATES PATENTS 2,882,326 4/1959 Jezl 208236 2,927,076 3/1960 Jolly 208237 3,016,349 1/1962 Oswald et al 208-254 DELBERT E. GANTZ, Primary Examiner.

S. P. JONES, Assistant Examiner. 

1. A PROCESS FOR TREATING HYDROCARBON FEED WHICH COMPRISES CONTACTING SAID FEED WITH A SOLUTION COMPRISING AN ORGANIC SULFOXIDE AND A NITROPHENOL, AND RECOVERING A HYDROCARBON PHASE HAING A SUBSTANTIALLY REDUCED NITROGEN CONTENT. 